Disc membranes are to be proteolytically digested with thermolysin. The F1-F2 noncovalent complex is to be prepared by chromatography on Concanavalin A-Sepharose. The F1 and F2 fragments will be individually prepared and compared to the F1-F2 complex. They will be characterized by SDS-gel electrophoresis, amino acid analysis and peptide mapping. The complete amino acid sequence of F2 will be determined, and the sequence analysis of F1 will be initiated. Functionally important sites of rhodopsin will be identified and located within the sequence of F1 and F2. These sites include the retinyl-lysine attachment site, the cysteine in F1 which is reactive toward N-ethylmaleimide in the dark, and the cysteine which is modified by iodoacetate following bleaching of rhodopsin. Methods will be developed which are required to perform the above objectives. These will include gel filtration separation of peptides on biogel P-100 in 70% formic acid, and application of a resin specific for binding arginyl-peptides for peptide separation.